Would this work for you? http://stooq.com/q/d/?s=3837.jp&c=0 As you can see the OHLC was adjusted for a split on 28 Sept. You can download the data to a csv file. You can go back as far as 1999 for some stocks. While you can't download all the stocks at once, you could use the non-adjusted source you have now and replace the data for the stocks that split, I guess, based on the list I sent you. There aren't that many each year, so it shouldn't be a big deal, I guess.
I don't know if http://stooq.com/q/d/?s=3837.jp&c=0 worked out for you or not, but in addition to dividends and normal splits, you might have noticed that it also adjusts for the changes in the trading unit from 1000 to 100 shares. All stocks must make that change by a date that I can't remember. That is the reason there were so many on 1 Oct. Once that's over things should be much easier for you as splits are not that common here. http://www.traders.co.jp/domestic_stocks/stocks_data/stock_change/stock_change.asp